Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 221013

Area Forecast Discussion
National Weather Service Salt Lake City UT
413 AM MDT Sat Oct 22 2016

.SYNOPSIS...An unseasonably warm southwest flow will exist across
the area this weekend. Moisture will spread north into Utah late
Sunday, and will continue to increase into early next week. Drier
conditions will return for the middle of the week.


.SHORT TERM (Until 00z Wednesday)...The axis of the upper ridge to
the east of Utah has left the forecast area under an unseasonably
warm and dry southwest flow aloft. A moderately strong near 700mb
flow along with adequate mixing should generate fairly strong
southerly winds across the southern and western valleys the next
couple of days.

GOES Pwat imagery shows a decent amount of moisture pooled over
southwest Arizona/northwest Mexico this morning. This moisture
will remain well south of the state through early Sunday, then
quickly move north into southwest Utah as the mean layer flow
backs and strengthens ahead of the upper trough advancing on the
west coast.

A few terrain-based showers could show up along the leading edge
of the moisture surge over southwest Utah late Sunday afternoon
through early evening. Model guidance does show a weak embedded
shortwave lift northeast into southern/central Utah Sunday night.
This feature will bring some expansion in areal coverage to
showers, though with lift still on the weak side would think that
precip amounts will remain on the light side.

A more substantial shortwave rotating out of the west coast trough
looks to bring more widespread and somewhat heavier precip to the
forecast area Monday through early Tuesday. This dynamic feature
will encounter rather substantial amounts of moisture by the time
it arrives in Utah. Convection could strengthen across western
and northern Utah Monday night as cooler mid-level air arrives and
the nose of the Pacific jet punches into the western Great Basin.

Showers will continue into Tuesday morning, with most of the
activity along the passing remnant of the shortwave across
northern and eastern Utah. Increasing dynamic subsidence and
building heights Tuesday afternoon should bring a rapid decreasing
trend to showers by late in the day.

.LONG TERM (After 00z Wednesday)...Ridging will be present at the
start of the long term portion of the forecast. A fairly robust
trough is expected to be approaching the Pacific Coast, helping to
shift the ridge eastward, and bringing increasing southwesterly flow
to the area Wednesday.

Given the ridge remains in place across the southern Rockies and
southern Plains, the trough is expected to split across the West
Friday. Right now, the split occurs in a position to still bring a
fairly robust system through Utah Friday.

Global models continue to have timing differences in the evolution
of this trough as well as when/if the trough will split. With a
significant disparity between various global model solutions,
started increasing pops in the extended, particularly Friday, though
did not raise pops nearly as high as the GFS in particular would
indicate. If model to model and run to run consistency increases
with the evolution of this pattern and the split occurs in a favored
location, Utah may be in store for a fairly significant
precipitation event. Confidence is low at this time, however.


.AVIATION...Light southerly winds will become northwesterly at the
SLC terminal between 18-20Z. Otherwise, high pressure remains in





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